A microwave monolithic integrated circuit (MMIC) is used in a transmitter and a receiver of various types of radio systems such as portable communication systems, military communication systems, satellite communication systems, and the like. The MMIC is manufactured through a semiconductor manufacturing process and is formed in an unpacked bare chip. Therefore, the MMIC needs an appropriate package.
A highly efficient package for MMIC of microwaves and millimeter waves must satisfy mechanical, electrical, and environmental requirements. In an aspect of mechanical and environmental requirements, the package must provide a function of protecting an internal circuit from surrounding environments. In an aspect of electrical requirements, the package must provide a minimum insertion loss and a high isolation between terminals and also provide a function of shielding electromagnetic waves in order to reduce electromagnetic interference (EMI). Also, another important electrical requirement is to not allow the package to give an adverse effect on a circuit performance or to make parasitic cavity resonance deteriorate the circuit performance.
Generally, an internal circuit mounted onto a surface mount package may be electrically connected with an external circuit by vertical interconnection and also may need a low-loss vertical interconnection in order to completely transfer signals of a microwave band and a millimeter wave band.